Unless your iOS version has somehow become corrupted, i can't understand why the toggle would be present and then all of a sudden disappear, but I'm not there. You may have to restore the device via iTunes and then set it up as a new device, however, if you do that and you do not know the iCloud credentials, you will be unable to use it until you enter the credentials. With that in mind, if you're a kid trying to bypass the restrictions set by your parents that prevents you from using FaceTime and/or iMessage, deal with it until you're an adult and can buy your own i-Device...